Originally Posted by
navi tasan
1-Their work should be over by the time we arrive. My inference with this out of context statement is that there is a likelihood that the work will be finished.
2-Their work has to be over by the time we arrive. Obligation or strong probability as in "They have been working on this for three days. It must be over by the time we arrive". Context.
3-Their work must be over by the time we arrive. Same as above.
4-They should finish their work by the time we arrive. I don't like the way this is stated. For likelihood: "They should have finished the work by the time we arrive". For obligation: "The work must be finished by the time we arrive" or as in #5..
5-They have to finish their work by the time we arrive. Obligation. But I don't like this either. I would rather, "They have (have got) to have finished etc."
6- They must finish their work by the time we arrive. Obligation but prefer "must have finished" and could be "a" or "b"
a-an inference and the idea of likelihood (their work will very probably be over by that time)
and which:
b-an obligation (it is their obligation to finish their work by that time)
Gratefully,
Navi,